Enroute Diversions & Lost Communications

Lost Communications — 14 CFR 91.185

Two-way radio communications failure in IFR conditions is a situation every instrument pilot must be prepared to handle. The regulation provides a structured decision tree so both you and ATC can predict each other's actions.

Step 1: Squawk 7600

Immediately set your transponder to 7600. This tells ATC you have lost communications. They will begin protecting airspace for you based on what they expect you to do under 91.185.

Step 2: VFR or IFR Conditions?

If the failure occurs in VFR conditions, or if VFR conditions are encountered after the failure, continue the flight under VFR and land as soon as practicable. The regulation is clear — if you can see, get on the ground. The lost comms procedures below apply only when you are in IMC and must remain IFR.

Step 3: Route — AVE-F

If you must continue IFR, fly the route in the following priority order (14 CFR 91.185(c)(1)):

Step 4: Altitude — Highest Of

For each route segment, fly at the highest of the following three altitudes (14 CFR 91.185(c)(2)):

This rule protects you from terrain and from conflicting traffic. ATC uses the same rule to predict your altitude and clear other aircraft out of your way.

Step 5: When to Begin the Approach

At your destination, leave the clearance limit (or holding fix) and begin the approach at the later of:

• EFC time: If you received an Expect Further Clearance time, leave the fix at the EFC time
• Expected arrival time: If no EFC was given, leave at the time you would have expected to arrive based on your filed or amended Estimated Time Enroute (ETE)

IFR Fuel Minimums

No person may operate a civil aircraft in IFR conditions unless it carries enough fuel to (14 CFR 91.167):

1. Complete the flight to the first airport of intended landing
2. Fly from that airport to the alternate airport (if an alternate is required)
3. Fly for 45 minutes at normal cruising speed after that

This is a planning requirement. You must have this fuel at the time of departure. If conditions change enroute and you no longer meet this requirement, you need to take action — divert or declare minimum fuel.

Alternate Airport Requirements — The 1-2-3 Rule

An alternate airport must be listed on your IFR flight plan unless the weather at the destination meets the 1-2-3 criteria (14 CFR 91.169(b)):

If the destination forecast does not meet all three criteria, you must file an alternate. The alternate itself must meet separate weather minimums: for a precision approach, 600-2 (600 ft ceiling, 2 SM visibility); for a non-precision approach, 800-2.

NW KRAFT — Preflight Weather Briefing

Before every IFR flight, systematically gather the information that affects your go/no-go decision:

IFR Diversion Procedures on the G1000

When ATC issues a reroute or you need to divert, you have three primary methods on the G1000:

Direct-To

The fastest method. Press the Direct-To key, enter the waypoint identifier, and activate. This creates a magenta course line directly to the fix. Use this when ATC says "proceed direct" to a single fix.

Editing the Flight Plan Enroute

For complex reroutes (e.g., "direct SAX, V252, GDM, as filed"), you need to edit your active flight plan:

1. Open the FPL page
2. Cursor to the point where the new route begins
3. Insert new waypoints and airways
4. Delete waypoints that are no longer part of the route
5. Activate the modified flight plan

Practice this on the ground first. Editing a flight plan in turbulence at 8,000 feet requires familiarity with the interface.

OBS Mode

OBS (Omni-Bearing Selector) mode suspends automatic waypoint sequencing and allows you to set a specific course to or from the current waypoint. Useful when ATC assigns a specific heading to intercept a radial or when holding on a specific course.

EFC Logic — Expect Further Clearance

When ATC places you in a hold, they issue an Expect Further Clearance (EFC) time. This time serves two critical purposes:

1. Normal operations: It tells you approximately how long the delay will be. ATC will issue new clearance before the EFC time.
2. Lost comms: If you lose communications while holding, the EFC time tells you when to leave the hold and proceed to your destination. This is the mechanism that allows ATC to predict your behavior.

Transponder Emergency Codes

Three transponder codes are reserved for emergencies. Know them cold:

Flight Overview

Today's simulator session flies from Morristown Municipal (KMMU) to Syracuse Hancock International (KSYR). During the flight, you will receive an ATC reroute, hold at Sparta VOR (SAX) with a crosswind, and then experience a simulated communications failure requiring you to apply the full 14 CFR 91.185 decision tree.

Phase 1: Departure & ATC Reroute

1. Depart KMMU IFR: Copy your clearance, brief the departure procedure, and depart
2. Receive ATC reroute: After departure, New York Center issues: "N12345, reroute — proceed direct Sparta, Victor 252 to Gardner, then as filed."
3. Read back: Confirm the full reroute clearance
4. Reprogram the G1000: Use Direct-To for SAX, then edit the flight plan to add V252 and GDM. This is your primary avionics management task — practice it until it becomes routine

Phase 2: Hold at SAX with EFC

Upon reaching the Sparta VOR, ATC places you in a hold:

"N12345, hold northwest of Sparta on the 330 radial, right turns, expect further clearance at 1545 Zulu."

1. Determine entry: Based on your inbound heading, select the correct hold entry (direct, teardrop, or parallel)
2. Set up the hold: Program the holding pattern in the G1000 or use OBS mode to track the inbound course
3. Wind correction: With a 15-knot crosswind, adjust your outbound heading to compensate. On the outbound leg, turn into the wind. On the inbound leg, let the correction bring you back to the holding course
4. Note the EFC time: Write it down. In the event of lost comms, this is when you leave the hold
5. Timing: Standard 1-minute outbound legs above 14,000 ft (or 1.5 minutes). Adjust outbound timing to achieve 1-minute inbound legs

Phase 3: Lost Communications Simulation

While holding at SAX, your instructor will simulate a communications failure. From this point forward, apply the 91.185 decision tree:

Immediate Actions

1. Squawk 7600
2. Attempt communication on all available frequencies — last assigned, 121.5, FSS
3. Try your backup radio (COM 2)
4. Check headset connections, audio panel settings, and circuit breakers

Decision Tree

1. VFR or IFR? — The scenario is IMC, so continue IFR
2. Route (AVE-F): You were assigned "direct SAX, V252, GDM, then as filed." This is your last assigned route — follow it
3. Altitude: For each segment, fly the highest of MEA, expected altitude, or assigned altitude
4. When to leave the hold: You received an EFC of 1545Z — depart SAX at 1545Z and proceed on your route
5. When to begin the approach at KSYR: Arrive and begin the approach. If the clearance limit is the airport (which it is), no additional holding is required at the destination

Phase 4: G1000 Flight Plan Management

Practice both methods of handling a reroute:

Method 1: Direct-To

• Press Direct-To, enter the fix identifier, and activate
• Best for simple "proceed direct" clearances to a single fix
• Limitation: does not modify the rest of your flight plan — after the Direct-To fix, the G1000 sequences to the next waypoint in your original flight plan

Method 2: Full Reroute via Flight Plan Edit

• Open FPL, insert new waypoints and airways, delete old ones
• Use for complex reroutes with multiple segments
• Verify the route looks correct on the MFD map before activating
• This is slower but ensures your G1000 navigation matches your actual clearance for the entire route

OBS Mode

• Press the OBS key to suspend waypoint sequencing
• Set the desired course to/from the active waypoint
• Useful for holding, tracking a specific radial, or when ATC assigns "maintain present heading, intercept the 180 radial of SAX"

ATC Communication Audio

Listen to and practice with these recorded ATC communications for this lesson:

• Pre-flight ATIS / Briefing
• Pilot Initial Call
• ATC Response
• ATC Clearance (Reroute)
• Pilot Readback
• ATC Confirmation

Key Takeaways

1. Lost comms procedure starts with 7600. Squawk 7600 immediately. Then attempt all available frequencies — last assigned, 121.5, COM 2, FSS. Check headset, audio panel, and circuit breakers before committing to nordo operations.
2. AVE-F determines your route. Assigned, Vectored, Expected, Filed — in priority order. Fly the highest-priority route that applies. This is not a sequential checklist; it is a hierarchy.
3. Altitude rule: fly the highest of three. For each segment, fly the highest of the Minimum Enroute Altitude, the altitude you were told to expect, and the altitude you were last assigned. This can change with each route segment.
4. Squawk 7600 is lost comms, not an emergency. 7500 is hijack. 7700 is general emergency. Never cycle through 7500 when changing codes — ATC radar triggers immediately.
5. EFC time governs when you leave the hold. If you received an Expect Further Clearance time and lose comms, depart the holding fix at the EFC time. If no EFC was given, proceed based on your expected arrival time.
6. Diversions require G1000 proficiency. Direct-To handles simple reroutes. Full flight plan edits handle complex ones. OBS mode suspends waypoint sequencing for holding or radial intercepts. Practice all three on the ground.
7. IFR fuel planning is non-negotiable. Destination + alternate + 45 minutes at normal cruise. Know the 1-2-3 rule for when you need an alternate, and the 600-2 / 800-2 minimums for alternate weather.

Oral Exam Self-Test

Lost communications is one of the most heavily tested topics on the instrument oral exam. You should be able to answer every one of these questions from memory.

1. What regulation governs two-way radio communications failure during IFR flight? What does it require?
2. What is the first thing you do when you realize you have lost communications in IMC?
3. If you lose communications in VFR conditions, what does the regulation require?
4. Explain AVE-F. What does each letter stand for, and how do you apply the hierarchy?
5. You were assigned 6,000, told to expect 8,000, and the MEA on your current segment is 5,000. You lose comms. What altitude do you fly? What if the MEA on the next segment is 10,000?
6. You are being radar vectored to intercept V16 when you lose comms. What route do you fly?
7. You are holding at a fix with an EFC of 1530Z when you lose comms at 1515Z. When do you leave the fix?
8. Your clearance limit is the destination airport. You arrive and the weather is IMC. Do you hold or begin the approach?
9. What are the three emergency transponder codes? What does each mean?
10. What is the IFR fuel requirement under 14 CFR 91.167? State the complete formula.
11. What is the 1-2-3 rule? When does it apply, and what are the alternate airport weather minimums for precision and non-precision approaches?
12. You filed a route of KMMU direct SAX V252 GDM direct KSYR. After departure, ATC clears you "direct SAX, V252, GDM, then as filed." Enroute, ATC says "expect direct KSYR after GDM." You lose comms after GDM. What route do you fly — direct KSYR or as filed?

Pilot Preparation for Lesson 9

Lesson 9 covers emergencies, system failures, and partial panel flying.

Reading

1. Everything Explained: Emergency Procedures section (complete)
2. Instrument Flying Handbook: Chapter on unusual attitudes, partial panel, and emergency operations
3. 14 CFR 91.3: Responsibility and authority of the pilot in command (emergency authority)
4. 14 CFR 91.185: Review once more — emergencies and lost comms often overlap
5. AIM 6-3-1 through 6-3-5: Distress and urgency procedures

Key Topics to Preview

• Vacuum system failure — recognizing the symptoms, which instruments are affected
• Partial panel flying — controlling the aircraft with limited instruments
• Unusual attitude recovery under the hood
• Electrical failure — load shedding, battery endurance, alternator checks
• Pitot-static system failures — blocked pitot tube, blocked static port
• Engine failure in IMC — immediate actions, nearest suitable airport
• Declaring an emergency — when and how, and why you should not hesitate

Resources

• Instrument Rating Files — Lost communications flowchart, diversion planning reference, alternate airport data
• Instrument Flying Handbook (FAA-H-8083-15B)
• 14 CFR 91.185 — Full Regulation Text